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Off-label use of letrozole in Chinese short pubertal boys: Effectiveness, safety, and exposure-response analysis
Yuan Xu1,2, Yan-Hong Zhang3,4, Qiu-Ping Zhang3,4
1Department of Clinical Pharmacy, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, China.
Insights
Letrozole treatment improved predicted adult height in Chinese boys with short puberty. This study assessed its effectiveness and safety, noting potential adverse reactions and establishing an exposure-response relationship for personalized therapy.
Area of Science:
- Pediatric Endocrinology
- Pharmacology
- Clinical Trial Research
Background:
- Letrozole is used off-label for short pubertal boys, but data primarily comes from Caucasian populations.
- Ethnic differences necessitate specific studies for Chinese pediatric populations.
Purpose of the Study:
- Evaluate letrozole effectiveness and safety in Chinese short pubertal boys.
- Establish an exposure-response relationship for letrozole in this demographic.
Main Methods:
- 41 Chinese boys received daily letrozole (2.5 mg) with growth hormone.
- Follow-up at 1, 3, 6, and 12 months with plasma sample analysis via HPLC.
Main Results:
- 88% of boys showed increased predicted adult height after 1 year.
- Predicted adult height increased significantly (168.4 to 173.0 cm), with decreased estrogen levels.
- Adverse drug reactions occurred in 22% of participants.
Conclusions:
- Letrozole shows effectiveness in increasing predicted adult height in Chinese boys.
- Further optimization and personalized therapies are needed for letrozole treatment in this population.
Aims:
Recently, letrozole has been used off-label to treat short pubertal boys. The experience on letrozole effectiveness and safety has been obtained primarily from Caucasian children. A simple extrapolation of the data to Chinese paediatric populations is questionable because of the substantial ethnic differences between the two populations. Therefore, the present study aimed to determine the effectiveness and safety of letrozole use in Chinese short pubertal boys as well as to establish an exposure-response relationship.
Methods:
Forty-one Chinese boys were included in the study. Patients were given letrozole tablets (2.5 mg) once daily in combination with growth hormone, and follow-up visits were made after 1, 3, 6 and 12 months of treatment. Plasma samples were taken from clinical examinations and analysed using high performance liquid chromatography with fluorescence detection.
Results:
After 1 year of treatment, 35 (88%) boys showed increased predicted adult heights. However, possible adverse drug reactions were seen in nine boys (22%). Predicted adult heights increased significantly from 168.4 ± 3.7 to 173.0 ± 4.2 cm, while oestrogen levels dropped from 33.2 ± 7.4 to 21.6 ± 7.3 pg/mL. Increments in predicted adult height were significantly correlated with trough letrozole concentrations (r = 0.39, P = .01).
Conclusion:
Letrozole treatment in Chinese pubertal populations should be further optimized, and more personalized therapies should be developed.
